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According to Oracle's documentation, third normal form schemas "may require less data-transformation than more normalized schemas such as star schemas".

I'm confused, I thought 3NF is the most normalized among common schema models, then goes snowflake schema and at last star schema.

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Perhaps it's a typo and they meant "less normalized schemas ..." –  ypercube Sep 7 '12 at 12:12
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"3NF is the most normalized among common schema models", this is not true as there are more normal forms than 3. –  Emmad Kareem Sep 7 '12 at 21:56
    
3NF is the most common though, I think that's what @Yrogirg meant. –  Valentino Vranken Apr 12 '13 at 6:10

1 Answer 1

up vote 2 down vote accepted

As @ypercube stated this seems to be a typo and should be changed to "more de-normalized schemas". One of the following paragraphsinthe Oracle manual states:

Snowflake schemas normalize dimensions to eliminate redundancy. That is, the dimension data has been grouped into multiple tables instead of one large table. For example, a product dimension table in a star schema might be normalized into a products table, a product_category table, and a product_manufacturer table in a snowflake schema.

This product dimension table of the star schema described here is not in third normal form but are results of joining (denormalize) some tables of the snowflake schema.

I found aricles on the web that describe why a star schema is not in 3rd normal form link link

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